LEDs and OLEDs are current-controlled devices where the intensity of light emitted from the device is related to the amount of current driven through the device. It is therefore highly advantageous to carefully and reliably control the amount of current flowing through the LED or OLED device(s) in order to achieve the desired illumination effect from an illumination system and to maximise the life of a device by ensuring the maximum current or power specifications are not exceeded. In addition it is well known that the switching or modulation speed of LED and OLED devices are fast enough to enable their use as data transmitters in combination with the primary use of illumination.
(O)LED power supply systems have been developed based on a variety of circuit design topologies which provide the ability to vary the actual or time-averaged forward current through the light emitting device load over an acceptable range in order to provide dimming capabilities. (O)LED illumination systems have been devised which, through the use of multiple light emitting devices having discrete wavelengths/colours, can produce a variety of colours and intensities. Systems incorporating Red, Green, Blue, Amber and White light emitters can create near infinite colour variations by varying the intensity, current or power of each of the coloured light emitter(s) individually or together in combination. The use of multiple discrete wavelengths in the illumination system provides the opportunity to increased data transfer rate from the light emitting devices by using different photon energies multiplexed simultaneously to increase system bandwidth.